#include <Adafruit_NeoPixel.h> 
int PIN =12;
int N_LEDS =16;
Adafruit_NeoPixel ring = Adafruit_NeoPixel(N_LEDS, PIN);

void setup() 
{
  ring.begin();
}

void loop()
 {
  for(int i=0; i<N_LEDS; i++ ) 
  {
    ring.setPixelColor(i , ring.Color(90, 0, 255));
    ring.show();
    delay(500);

    ring.setPixelColor(i , ring.Color(155, 155, 155)); // 
    ring.show();
    delay(500);
  }
 }